Identifying asynchronous power loss

ABSTRACT

Apparatus having an array of memory cells include a controller configured to read a particular memory cell of a last written page of memory cells of a block of memory cells of the array of memory cells, determine whether a threshold voltage of the particular memory cell is less than a particular voltage level, and mark the last written page of memory cells as affected by power loss during a programming operation of the last written page of memory cells when the threshold voltage of the particular memory cell is determined to be higher than the particular voltage level.

RELATED APPLICATION

This Application is a Continuation of U.S. application Ser. No.15/911,490, titled “IDENTIFYING ASYNCHRONOUS POWER LOSS,” filed Mar. 5,2018, which is a Continuation of U.S. application Ser. No. 15/390,833,titled “IDENTIFYING ASYNCHRONOUS POWER LOSS,” filed Dec. 27, 2016, nowU.S. Pat. No. 9,921,898, issued on Mar. 20, 2018, which are commonlyassigned and incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to memory and, in particular,in one or more embodiments, the present disclosure relates to apparatusand methods to identify asynchronous power loss.

BACKGROUND

Memory devices are typically provided as internal, semiconductor,integrated circuit devices in computers or other electronic devices.There are many different types of memory including random-access memory(RAM), read only memory (ROM), dynamic random access memory (DRAM),synchronous dynamic random access memory (SDRAM), and flash memory.

Flash memory has developed into a popular source of non-volatile memoryfor a wide range of electronic applications. Flash memory typically usea one-transistor memory cell that allows for high memory densities, highreliability, and low power consumption. Changes in threshold voltage(Vt) of the memory cells, through programming (which is often referredto as writing) of charge storage structures (e.g., floating gates orcharge traps) or other physical phenomena (e.g., phase change orpolarization), determine the data state (e.g., data value) of eachmemory cell. Common uses for flash memory and other non-volatile memoryinclude personal computers, personal digital assistants (PDAs), digitalcameras, digital media players, digital recorders, games, appliances,vehicles, wireless devices, mobile telephones, and removable memorymodules, and the uses for non-volatile memory continue to expand.

A NAND flash memory is a common type of flash memory device, so calledfor the logical form in which the basic memory cell configuration isarranged. Typically, the array of memory cells for NAND flash memory isarranged such that the control gate of each memory cell of a row of thearray is connected together to form an access line, such as a word line.Columns of the array include strings (often termed NAND strings) ofmemory cells connected together in series between a pair of selectgates, e.g., a source select transistor and a drain select transistor.Each source select transistor may be connected to a source, while eachdrain select transistor may be connected to a data line, such as columnbit line. Variations using more than one select gate between a string ofmemory cells and the source, and/or between the string of memory cellsand the data line, are known.

In programming memory, memory cells may generally be programmed as whatare often termed single-level cells (SLC) or multiple-level cells (MLC).SLC may use a single memory cell to represent one digit (e.g., bit) ofdata. For example, in SLC, a Vt of 2.5V might indicate a programmedmemory cell (e.g., representing a logical 0) while a Vt of −0.5V mightindicate an erased cell (e.g., representing a logical 1). MLC uses morethan two Vt ranges, where each Vt range indicates a different datastate. Multiple-level cells can take advantage of the analog nature of atraditional charge storage cell by assigning a bit pattern to a specificVt range. While MLC typically uses a memory cell to represent one datastate of a binary number of data states (e.g., 4, 8, 16, . . . ), amemory cell operated as MLC may be used to represent a non-binary numberof data states. For example, where the MLC uses three Vt ranges, twomemory cells might be used to collectively represent one of eight datastates.

In programming MLC memory, data values are often programmed using morethan one pass, e.g., programming one or more digits in each pass. Forexample, in four-level MLC (typically referred to simply as MLC), afirst digit, e.g., a least significant bit (LSB), often referred to aslower page (LP) data, may be programmed to the memory cells in a firstpass, thus resulting in two (e.g., first and second) threshold voltageranges. Subsequently, a second digit, e.g., a most significant bit(MSB), often referred to as upper page (UP) data may be programmed tothe memory cells in a second pass, typically moving some portion ofthose memory cells in the first threshold voltage range into a thirdthreshold voltage range, and moving some portion of those memory cellsin the second threshold voltage range into a fourth threshold voltagerange. Similarly, eight-level MLC (typically referred to as TLC) mayrepresent a bit pattern of three bits, including a first digit, e.g., aleast significant bit (LSB) or lower page (LP) data; a second digit,e.g., upper page (UP) data; and a third digit, e.g., a most significantbit (MSB) or extra page (XP) data. In operating TLC, the LP data and theUP data may be programmed to the memory cells in a first pass, resultingin four threshold voltage ranges, followed by the XP data (and,possibly, reprogramming of the UP data) in a second pass, resulting ineight threshold voltage ranges.

In each pass, programming typically utilizes an iterative process ofapplying a programming pulse to a memory cell and verifying if thatmemory cell has reached its desired data state in response to thatprogramming pulse, and repeating that iterative process until thatmemory cell passes the verification. Once a memory cell passes theverification, it may be inhibited from further programming. Theiterative process can be repeated with changing (e.g., increasing)voltage levels of the programming pulse until each memory cell selectedfor the programming operation has reached its respective desired datastate, or some failure is declared, e.g., reaching a maximum number ofallowed programming pulses during the programming operation.

Due to the nature of flash memory devices, the physical location withina flash memory device for a given logical address will generally changeover time. To address this changing correspondence, a Flash TranslationLayer (FTL) is typically used to map the logical address to the physicaladdress to which data has been stored. Although this high-level mappinginformation is often held in volatile memory for ease of use duringoperation of the memory device, such mapping information may also beperiodically stored to non-volatile memory so that it may be retrievedduring start-up of the device. Alternatively, this mapping informationmay be updated to non-volatile storage with each programming operation.If a memory device is powered down abruptly or otherwise loses power inan uncontrolled manner, e.g., asynchronous power loss, the most recentmapping information, as well as user data, may be invalid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a simplified block diagram of a memory in communication witha processor as part of an electronic system, according to an embodiment.

FIG. 1B is a simplified block diagram of an apparatus in the form of amemory module in communication with a host as part of an electronicsystem, according to another embodiment

FIGS. 2A-2C are schematics of portions of an array of memory cells ascould be used in a memory of the type described with reference to FIG.1A.

FIG. 3 is a representation of a page of memory cells for use withembodiments.

FIG. 4 is a representation of blocks of memory cells for use withembodiments.

FIGS. 5A-5B depict representations of populations of memory cells atvarious stages of a programming operation according to an embodiment.

FIGS. 6-9 are flowcharts of methods of operating an apparatus accordingto embodiments.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown, byway of illustration, specific embodiments. In the drawings, likereference numerals describe substantially similar components throughoutthe several views. Other embodiments may be utilized and structural,logical and electrical changes may be made without departing from thescope of the present disclosure. The following detailed description is,therefore, not to be taken in a limiting sense.

If an apparatus detects that a connected or component memory hassuffered an uncontrolled shut-down, such as by reading a system flag atpower-up of the memory, the apparatus may seek to detect whether a powerloss occurred during a programming operation. Current algorithms usedfor such power-loss detection rely on margin reads and error handlingroutines. For example, when power loss is suspected, an algorithm maycause the memory device to read all pages to determine the last writtenpage of memory cells in a block of memory cells. This last written pageof memory cells may then be checked to determine if a power lossoccurred during programming. This can be determined by adding a positiveor negative offset to one or more read voltages prior to initiating aread on the questionable page of memory cells, a process referred to asa margin read. These margin reads might be performed in one readoperation or multiple read operations on the same page of memory cells.Differentiating between power loss during a programming operation versusmerely a data retention issue may be accomplished by applying a negativeoffset to the read voltage for the data state corresponding to at leastthe highest range of threshold voltages. If, after performing thismargin read, error handling routines are unable to recover the data fromthe questionable page, that page of memory cells and its data are deemedto be affected by power loss.

Such algorithms, e.g., both margin read and error handling algorithms,used for detection generally become increasingly complex as the numberof bits per memory cell increase. This can detrimentally impact power-upperformance of the memory, as well as increase firmware complexity andcost. Furthermore, this process may be repeated in response to multiplepower-loss events, even for pages of memory cells that were previouslydetermined to be affected by power loss.

In addition, in solid state drives (SSDs), blocks of memory cells frommultiple memories are often logically combined into a super block, e.g.,a block of memory cells from each respective memory device. In olderSSDs, when a block of memory cells was determined to be affected bypower loss, its super block was queued for garbage collection, meaningthat good data from the super block would be transferred to a new superblock, and the super block containing the affected page of memory cellswould be marked as intended for later erase and reuse, even if itcontained a large amount of unused capacity. Without such treatment, anaffected block of memory cells might have to be subjected to thedetection and error correction algorithms in response to each power lossevent. As super blocks become larger and fewer, this premature queuingof a super block for garbage collection removes larger amounts of memoryfrom immediate availability, and may cause the SSD to go into writeprotect or have poor performance during the recovery process. It maythus be desirable to avoid queuing a super block for garbage collectionwhen usable pages of memory cells are still available.

Various embodiments seek to identify pages of memory cells affected bypower loss, and to mark such pages of memory cells for future tracking.By changing a desired data state of a memory cell of a group of memorycells being programmed when a power loss is detected, a value may bestored within that group of memory cells that can indicate the powerloss without requiring any margin read operations. This can facilitateimprovements in the time required to recover from a power loss event.

FIG. 1A is a simplified block diagram of a first apparatus, in the formof a memory (e.g., memory device) 100, in communication with a secondapparatus, in the form of a processor 130, and a third apparatus, in theform of a power supply 136, as part of a fourth apparatus, in the formof an electronic system, according to an embodiment. For someembodiments, the power supply 136 may be external to an electronicsystem containing the processor 130 and the memory device 100. Someexamples of electronic systems include personal computers, personaldigital assistants (PDAs), digital cameras, digital media players,digital recorders, games, appliances, vehicles, wireless devices, mobiletelephones, removable memory modules and the like. The processor 130,e.g., a controller external to the memory device 100, may represent amemory controller or other external host device.

Memory device 100 includes an array of memory cells 104 logicallyarranged in rows and columns. Memory cells of a logical row aretypically connected to the same access line (commonly referred to as aword line) while memory cells of a logical column are typicallyselectively connected to the same data line (commonly referred to as abit line). A single access line may be associated with more than onelogical row of memory cells and a single data line may be associatedwith more than one logical column. Memory cells (not shown in FIG. 1A)of at least a portion of array of memory cells 104 are arranged instrings of series-connected memory cells.

A row decode circuitry 108 and a column decode circuitry 110 areprovided to decode address signals. Address signals are received anddecoded to access the array of memory cells 104. Memory device 100 alsoincludes input/output (I/O) control circuitry 112 to manage input ofcommands, addresses and data to the memory device 100 as well as outputof data and status information from the memory device 100. An addressregister 114 is in communication with I/O control circuitry 112 and rowdecode circuitry 108 and column decode circuitry 110 to latch theaddress signals prior to decoding. A command register 124 is incommunication with I/O control circuitry 112 and control logic 116 tolatch incoming commands.

A controller, such as an internal controller (e.g., control logic 116),controls access to the array of memory cells 104 in response to thecommands and generates status information for the external processor130, i.e., control logic 116 may be configured to perform accessoperations (e.g., programming operations) in accordance with embodimentsdescribed herein. The control logic 116 is in communication with rowdecode circuitry 108 and column decode circuitry 110 to control the rowdecode circuitry 108 and column decode circuitry 110 in response to theaddresses.

Control logic 116 is also in communication with a cache register 118 anddata register 120. Cache register 118 latches data, either incoming oroutgoing, as directed by control logic 116 to temporarily store datawhile the array of memory cells 104 is busy writing or reading,respectively, other data. During a programming operation (e.g., oftenreferred to as a write operation), data is passed from the cacheregister 118 to the data register 120 for transfer to the array ofmemory cells 104; then new data is latched in the cache register 118from the I/O control circuitry 112. During a read operation, data ispassed from the cache register 118 to the I/O control circuitry 112 foroutput to the external processor 130; then new data is passed from thedata register 120 to the cache register 118. A status register 122 is incommunication with I/O control circuitry 112 and control logic 116 tolatch the status information for output to the processor 130.

Memory device 100 receives control signals at control logic 116 fromprocessor 130 over a control link 132. The control signals may includeat least a chip enable CE#, a command latch enable CLE, an address latchenable ALE, a write enable WE#, and a write protect WP#. Additionalcontrol signals (not shown) may be further received over control link132 depending upon the nature of the memory device 100. Memory device100 receives command signals (which represent commands), address signals(which represent addresses), and data signals (which represent data)from processor 130 over a multiplexed input/output (I/O) bus 134 andoutputs data to processor 130 over I/O bus 134.

For example, the commands are received over input/output (I/O) pins[7:0] of I/O bus 134 at I/O control circuitry 112 and are written intocommand register 124. The addresses are received over input/output (I/O)pins [7:0] of bus 134 at I/O control circuitry 112 and are written intoaddress register 114. The data are received over input/output (I/O) pins[7:0] for an 8-bit device or input/output (I/O) pins [15:0] for a 16-bitdevice at I/O control circuitry 112 and are written into cache register118. The data are subsequently written into data register 120 forprogramming the array of memory cells 104. For another embodiment, cacheregister 118 may be omitted, and the data are written directly into dataregister 120. Data are also output over input/output (I/O) pins [7:0]for an 8-bit device or input/output (I/O) pins [15:0] for a 16-bitdevice.

Memory device 100 and/or processor 130 may receive power from the powersupply 136. Power supply 136 may represent any combination of circuitryfor providing power to memory device 100 and/or processor 130. Forexample, power supply 136 might include a stand-alone power supply(e.g., a battery), a line-connected power supply (e.g., a switched-modepower supply common in desktop computers and servers or an AC adaptercommon for portable electronic devices), or a combination of the two.

Power is typically received from the power supply 136 using two or morevoltage supply nodes 137, such as a supply voltage node (e.g., Vcc) anda reference voltage node (e.g., Vss or ground). It is not uncommon for apower supply 136 to provide more than two voltage supply nodes 137. Forexample, a common standard for switched-mode power supplies, ATX(Advanced Technology eXtended) 2.x, provides, using a 28-pin connection,four voltage supply nodes (or pins) at +3.3V, five voltage supply nodesat +5V, four voltage supply nodes at +12V, one voltage supply node at12V, and ten voltage supply nodes at a reference voltage (e.g., 0V). TheATX 2.x standard further provides a power-on node for activating theforegoing voltage supply nodes when it is pulled to ground by anexternal circuit, a standby voltage supply node driven to +5V regardlessof whether the other voltage supply nodes are being driven to theirrespective voltage levels (which can be used to power the externalcircuit responsible for pulling the power-on node to ground), and apower-good node for indicating when the other voltage supply nodes arestabilized at their respective voltages. The remaining pin of the ATX2.x 28-pin standard is undefined. Memory device 100 and processor 130may utilize differing combinations of voltage supply nodes 137 frompower supply 136 depending upon their respective power needs. Forsimplicity, distribution of power from the voltage supply nodes 137 tocomponents within the memory device 100 is not depicted.

The voltage supply nodes 137, or other components of the electronicsystem, may have an inherent or added energy storage device, such ascapacitance 138, e.g., a hold-up capacitance, that can provide power tothe memory device 100, and optionally to the processor 130, for somefinite amount of time in the case of failure or removal of the powersupply 136. Sizing of the capacitance 138 can be readily determinedbased on the power requirements of at least the memory device 100 forthe operations described herein. While the energy storage device isdepicted as the capacitance 138 in examples herein, the capacitance 138could alternatively represent a battery. Furthermore, while thecapacitance 138 is depicted to be external to the memory device 100, itcould alternatively be an internal component of the memory device 100.

It will be appreciated by those skilled in the art that additionalcircuitry and signals can be provided, and that the memory device 100 ofFIG. 1A has been simplified. It should be recognized that thefunctionality of the various block components described with referenceto FIG. 1A may not necessarily be segregated to distinct components orcomponent portions of an integrated circuit device. For example, asingle component or component portion of an integrated circuit devicecould be adapted to perform the functionality of more than one blockcomponent of FIG. 1A. Alternatively, one or more components or componentportions of an integrated circuit device could be combined to performthe functionality of a single block component of FIG. 1A.

Additionally, while specific I/O pins are described in accordance withpopular conventions for receipt and output of the various signals, it isnoted that other combinations or numbers of I/O pins may be used in thevarious embodiments.

A given processor 130 may be in communication with one or more memorydevices 100, e.g., dies. FIG. 1B is a simplified block diagram of anapparatus in the form of a memory module 101 in communication with ahost 150 as part of an electronic system, according to anotherembodiment. Memory devices 100, processor 130, control link 132, I/O bus134, power supply 136, voltage supply nodes 137 and capacitance 138 maybe as described with reference to FIG. 1A. For simplicity, distributionof power from the voltage supply nodes 137 to the memory devices 100 andprocessor 130 within the memory module 101 is not depicted. Althoughmemory module (e.g., package) 101 of FIG. 1B is depicted with fourmemory devices 100 (e.g., dies), memory module 101 could have some othernumber of one or more memory devices 100.

Because processor 130 (e.g., a memory controller) is between the host150 and the memory devices 100, communication between the host 150 andthe processor 130 may involve different communication links than thoseused between the processor 130 and the memory devices 100. For example,the memory module 101 may be an Embedded MultiMediaCard (eMMC) of asolid state drive (SSD). In accordance with existing standards,communication with an eMMC may include a data link 152 for transfer ofdata (e.g., an 8-bit link), a command link 154 for transfer of commandsand device initialization, and a clock link 156 providing a clock signalfor synchronizing the transfers on the data link 152 and command link154. The processor 130 may handle many activities autonomously, such aspower-loss detection, error correction, management of defective blocks,wear leveling and address translation.

FIG. 2A is a schematic of a portion of an array of memory cells 200A ascould be used in a memory of the type described with reference to FIG.1A, e.g., as a portion of array of memory cells 104. Memory array 200Aincludes access lines, such as word lines 202 ₀ to 202 _(N), and a dataline, such as bit line 204. The word lines 202 may be connected toglobal access lines (e.g., global word lines), not shown in FIG. 2A, ina many-to-one relationship. For some embodiments, memory array 200A maybe formed over a semiconductor that, for example, may be conductivelydoped to have a conductivity type, such as a p-type conductivity, e.g.,to form a p-well, or an n-type conductivity, e.g., to form an n-well.

Memory array 200A might be arranged in rows (each corresponding to aword line 202) and columns (each corresponding to a bit line 204). Eachcolumn may include a string of series-connected memory cells, such asone of NAND strings 206 ₀ to 206 _(M). Each NAND string 206 might beconnected (e.g., selectively connected) to a common source 216 and mightinclude memory cells 208 ₀ to 208 _(N). The memory cells 208 mayrepresent non-volatile memory cells for storage of data. The memorycells 208 of each NAND string 206 might be connected in series between aselect gate 210 (e.g., a field-effect transistor), such as one of theselect gates 210 ₀ to 210 _(M) (e.g., that may be source selecttransistors, commonly referred to as select gate source), and a selectgate 212 (e.g., a field-effect transistor), such as one of the selectgates 212 ₀ to 212 _(M) (e.g., that may be drain select transistors,commonly referred to as select gate drain). Select gates 210 ₀ to 210_(M) might be commonly connected to a select line 214, such as a sourceselect line, and select gates 212 ₀ to 212 _(M) might be commonlyconnected to a select line 215, such as a drain select line. Althoughdepicted as traditional field-effect transistors, the select gates 210and 212 may utilize a structure similar to (e.g., the same as) thememory cells 208. The select gates 210 and 212 might represent aplurality of select gates connected in series, with each select gate inseries configured to receive a same or independent control signal.

A source of each select gate 210 might be connected to common source216. The drain of each select gate 210 might be connected to a memorycell 208 ₀ of the corresponding NAND string 206. For example, the drainof select gate 210 ₀ might be connected to memory cell 208 ₀ of thecorresponding NAND string 206 ₀. Therefore, each select gate 210 mightbe configured to selectively connect a corresponding NAND string 206 tocommon source 216. A control gate of each select gate 210 might beconnected to select line 214.

The drain of each select gate 212 might be connected to the bit line 204for the corresponding NAND string 206. For example, the drain of selectgate 212 ₀ might be connected to the bit line 204 ₀ for thecorresponding NAND string 206 ₀. The source of each select gate 212might be connected to a memory cell 208 _(N) of the corresponding NANDstring 206. For example, the source of select gate 212 ₀ might beconnected to memory cell 208 _(N) of the corresponding NAND string 206₀. Therefore, each select gate 212 might be configured to selectivelyconnect a corresponding NAND string 206 to the common bit line 204. Acontrol gate of each select gate 212 might be connected to select line215.

The memory array in FIG. 2A might be a three-dimensional memory array,e.g., where NAND strings 206 may extend substantially perpendicular to aplane containing the common source 216 and to a plane containing aplurality of bit lines 204 that may be substantially parallel to theplane containing the common source 216.

Typical construction of memory cells 208 includes a data-storagestructure 234 (e.g., a floating gate, charge trap, etc.) that candetermine a data state of the memory cell (e.g., through changes inthreshold voltage), and a control gate 236, as shown in FIG. 2A. Thedata-storage structure 234 may include both conductive and dielectricstructures while the control gate 236 is generally formed of one or moreconductive materials. In some cases, memory cells 208 may further have adefined source 230 and a defined drain 232. Memory cells 208 have theircontrol gates 236 connected to (and in some cases form) a word line 202.

A column of the memory cells 208 may be a NAND string 206 or a pluralityof NAND strings 206 selectively connected to a given bit line 204. A rowof the memory cells 208 may be memory cells 208 commonly connected to agiven word line 202. A row of memory cells 208 can, but need not,include all memory cells 208 commonly connected to a given word line202. Rows of memory cells 208 may often be divided into one or moregroups of physical pages of memory cells 208, and physical pages ofmemory cells 208 often include every other memory cell 208 commonlyconnected to a given word line 202. For example, memory cells 208commonly connected to word line 202 _(N) and selectively connected toeven bit lines 204 (e.g., bit lines 204 ₀, 204 ₂, 204 ₄, etc.) may beone physical page of memory cells 208 (e.g., even memory cells) whilememory cells 208 commonly connected to word line 202 _(N) andselectively connected to odd bit lines 204 (e.g., bit lines 204 ₁, 204₃, 204 ₅, etc.) may be another physical page of memory cells 208 (e.g.,odd memory cells). Although bit lines 204 ₃-204 ₅ are not explicitlydepicted in FIG. 2A, it is apparent from the figure that the bit lines204 of the array of memory cells 200A may be numbered consecutively frombit line 204 ₀ to bit line 204 _(M). Other groupings of memory cells 208commonly connected to a given word line 202 may also define a physicalpage of memory cells 208. For certain memory devices, all memory cellscommonly connected to a given word line might be deemed a physical pageof memory cells. The portion of a physical page of memory cells (which,in some embodiments, could still be the entire row) that is read duringa single read operation or programmed during a single programmingoperation (e.g., an upper or lower page of memory cells) might be deemeda logical page of memory cells. A block of memory cells may includethose memory cells that are configured to be erased together, such asall memory cells connected to word lines 202 ₀-202 _(N) (e.g., all NANDstrings 206 sharing common word lines 202). Unless expresslydistinguished, a reference to a page of memory cells herein refers tothe memory cells of a logical page of memory cells.

FIG. 2B is another schematic of a portion of an array of memory cells200B as could be used in a memory of the type described with referenceto FIG. 1A, e.g., as a portion of array of memory cells 104. Likenumbered elements in FIG. 2B correspond to the description as providedwith respect to FIG. 2A. FIG. 2B provides additional detail of oneexample of a three-dimensional NAND memory array structure. Thethree-dimensional NAND memory array 200B may incorporate verticalstructures which may include semiconductor pillars where a portion of apillar may act as a channel region of the memory cells of NAND strings206. The NAND strings 206 may be each selectively connected to a bitline 204 ₀-204 _(M) by a select transistor 212 (e.g., that may be drainselect transistors, commonly referred to as select gate drain) and to acommon source 216 by a select transistor 210 (e.g., that may be sourceselect transistors, commonly referred to as select gate source).Multiple NAND strings 206 might be selectively connected to the same bitline 204. Subsets of NAND strings 206 can be connected to theirrespective bit lines 204 by biasing the select lines 215 ₀-215 _(L) toselectively activate particular select transistors 212 each between aNAND string 206 and a bit line 204. The select transistors 210 can beactivated by biasing the select line 214. Each word line 202 may beconnected to multiple rows of memory cells of the memory array 200B.Rows of memory cells that are commonly connected to each other by aparticular word line 202 may collectively be referred to as tiers.

FIG. 2C is a further schematic of a portion of an array of memory cells200C as could be used in a memory of the type described with referenceto FIG. 1A, e.g., as a portion of array of memory cells 104. Likenumbered elements in FIG. 2C correspond to the description as providedwith respect to FIG. 2A. Array of memory cells 200C may include NANDstrings 206, word lines 202, bit lines 204, source select lines 214,drain select lines 215 and common source 216 as depicted in FIG. 2A. Thearray of memory cells 200A may be a portion of the array of memory cells200C, for example. FIG. 2C depicts groupings of NAND strings 206 intoblocks of memory cells 250. Blocks of memory cells 250 may be groupingsof memory cells 208 that may be erased together in a single eraseoperation, sometimes referred to as erase blocks.

FIG. 3 is a representation of a page of memory cells 300 for use withembodiments. The page of memory cells 300 is a group of memory cellsthat may be programmed concurrently during a single programmingoperation. For example, the page of memory cells 300 might include allor a subset of memory cells (e.g., memory cells 208 of FIG. 2A)connected to an access line (e.g., access line 202 ₁ of FIG. 2A).

The page of memory cells 300 includes a group of memory cells 310configured for storage of user data, e.g., memory cells addressable forstorage of user data. User data might include data received inassociation with a write command received by the memory to initiate aprogramming operation. The page of memory cells 300 further includes agroup of memory cells 312 configured for storage of overhead data(sometimes referred to as metadata), e.g., memory cells addressable forstorage of overhead data. Overhead data might include data generated bythe memory in response to a write command received by the memory. Forexample, overhead data might include status indicators, error correctioncode data, mapping information and the like. For example, statusindicators might include one or more flags 314, such as might be usedfor tracking progress of a programming operation. While the group ofmemory cells 310 and the group of memory cells 312 are each depicted tobe single contiguous groups of memory cells, memory cells of the groupof memory cells 310 might be interposed between memory cells of thegroup of memory cells 312, and vice versa, such that the group of memorycells 310 and/or the group of memory cells 312 may be non-contiguousgroups of memory cells.

With reference back to FIG. 1B, host 150 might transmit a write commandand associated data to the memory module 101, indicating a desire tostore the associated data to the memory module 101. The processor 130might then transmit a write command to the memory devices 100,indicating a desire to store the associated data to one or more of thememory devices 100 in a group of memory cells (e.g., of a page of memorycells) designated for storage of user data. The processor 130 mightfurther generate error correction code data for the user data, as wellas one or more flags or other overhead data to be stored to a group ofmemory cells (e.g., of the page of memory cells) designated for storageof overhead data concurrently with the storage of the user data to thegroup of memory cells designated for storage of user data.

FIG. 4 is a representation of blocks of memory cells for use withembodiments. As depicted in FIG. 4, each memory device 100 might includemultiple blocks of memory cells, e.g., each containing Blocks 0-N.Blocks of memory cells of multiple memory devices, e.g., Blocks 0 foreach memory device 100 ₀, 100 ₁ and 100 ₂, might be logically combinedto define a super block of memory cells 450. A super block of memorycells 450 might be formed for each corresponding block of memory cells(e.g., blocks of memory cells sharing the same logical address withintheir respective memory device 100) of the memory devices 100. Forexample, Blocks 1 for each memory device 100 might be logically combinedto define a super block of memory cells, Blocks 2 for each memory device100 might be logically combined to define a super block of memory cells,Blocks 3 for each memory device 100 might be logically combined todefine a super block of memory cells, etc. Although super block ofmemory cells 450 is depicted to include a block of memory cells fromeach of three memory devices 100, a super block could include blocks ofmemory cells from some other number of memory devices 100.

The page of memory cells 300 might represent a logical page of memorycells of a single block of memory cells 250 (e.g., of FIG. 2C), or itmight represent a logical page of memory cells of more than one block ofmemory cells, e.g., a super block of memory cells 450. Furthermore, apage of memory cells 300 representing a logical page of memory cells ofthe super block of memory cells 450 might contain user data and overheaddata in each block of memory cells (e.g., Block 0 of memory device 100₀, Block 0 of memory device 100 ₁, and Block 0 of memory device 100 ₂),or it might contain user data and/or overhead data in only a subset ofthe blocks of memory cells of the super block of memory cells 450. Forexample, user data of a page of memory cells 300 of the super block ofmemory cells 450 might be stored in Block 0 of memory device 100 ₀,Block 0 of memory device 100 ₁, and Block 0 of memory device 100 ₂, butoverhead data of that page of memory cells 300 might only be stored toBlock 0 of memory device 100 ₂.

FIGS. 5A-5B depict representations of populations of memory cells atvarious stages of a programming operation according to an embodiment.FIG. 5A may represent a first pass of a programming operation for a TLCmemory, e.g., having final data states each representing three digits ofinformation. FIG. 5B may represent a second pass of the programmingoperation for a TLC memory.

FIG. 5A includes a population of memory cells 500 having an initialthreshold voltage range. For example, the memory cells of a page ofmemory cells might be erased to each have a threshold voltage below aread voltage (e.g., a lowest read voltage) r011, and representing anerased data state. The first pass of a programming operation for a TLCmemory might involve loading lower page data, programming that lowerpage data, loading upper page data and programming that upper page data.As a result, the population of memory cells 500 might be programmed totheir respective desired data states corresponding to a population ofmemory cells 501 representing a first data state, a population of memorycells 502 representing a second data state, a population of memory cells503 representing a third data state, and a population of memory cells504 representing a fourth data state. The population of memory cells 501might represent a logical data value of ‘11’, the population of memorycells 502 might represent a logical data value of ‘01’, the populationof memory cells 503 might represent a logical data value of ‘00’, andthe population of memory cells 504 might represent a logical data valueof ‘10’, where the right-most digit might represent the lower page datafor a memory cell having a threshold voltage within the thresholdvoltage range of its respective population of memory cells and theleft-most digit might represent the upper page data for that memorycell. Although a specific example of binary representation is provided,embodiments may use other arrangements of bit patterns to represent thevarious data states.

A memory cell of the population of memory cells 500 configured forstorage of overhead data (e.g., a memory cell corresponding to flag 314₂ of FIG. 3) might be programmed to have a threshold voltage within thethreshold voltage range corresponding to a particular one of the fourdata states during the first pass of the programming operation. Forexample, as depicted by line 520, a memory cell of the population ofmemory cells 500 might have a desired data state corresponding to thepopulation of memory cells 503, e.g., a ‘00’ logical data value, for thefirst pass of the programming operation. Certain other memory cells ofthe population of memory cells 500 configured for storage of overheaddata (e.g., memory cells corresponding to flags 314 ₁ and 314 ₃ of FIG.3) might be inhibited from programming during the first pass of theprogramming operation, e.g., their desired data states might correspondto the population of memory cells 501, e.g., a ‘11’ logical data value,for the first pass of the programming operation. In this manner, memorycells corresponding to flags 314 ₁ and 314 ₃ of FIG. 3 each having thedata state corresponding to the population of memory cells 501, e.g., a‘11’ logical data value, and the memory cell corresponding to flag 314 ₂of FIG. 3 having the data state corresponding to the population ofmemory cells 503, e.g., a ‘00’ logical data value, can indicate to thememory that the first pass of the programming operation has beenperformed normally.

As is understood in the art, data states of memory cells within thepopulations of memory cells 501-504 may be determined by applying theread voltages r011, r101 and r000 and sensing for activation of thememory cells at the respective voltages. For example, memory cellsactivated in response to read voltage r011 would have the first datastate, any remaining memory cells activated in response to read voltager101 would have the second data state, any remaining memory cellsactivated in response to read voltage r000 would have the third datastate, and any remaining memory cells not activated in response to readvoltage r000 would have the fourth data state.

FIG. 5B includes the populations of memory cells 501-504 discussed withreference to FIG. 5A resulting from the first pass of a programmingoperation for a TLC memory. The second pass of the programming operationfor a TLC memory might involve loading extra page data and programmingthat extra page data based on knowledge of the current data state of thememory cell, such as by re-loading the prior data or reading the memorycell. As a result, the population of memory cells 501 might beprogrammed to their respective desired data states corresponding to apopulation of memory cells 511 representing a first data state, and apopulation of memory cells 512 representing a second data state; thepopulation of memory cells 502 might be programmed to their respectivedesired data states corresponding to a population of memory cells 513representing a third data state, and a population of memory cells 514representing a fourth data state; the population of memory cells 503might be programmed to their respective desired data statescorresponding to a population of memory cells 515 representing a fifthdata state, and a population of memory cells 516 representing a sixthdata state; and the population of memory cells 504 might be programmedto their respective desired data states corresponding to a population ofmemory cells 517 representing a seventh data state, and a population ofmemory cells 518 representing a eighth data state.

The population of memory cells 511 might represent a logical data valueof ‘111’, the population of memory cells 512 might represent a logicaldata value of ‘011’, the population of memory cells 513 might representa logical data value of ‘001’, the population of memory cells 514 mightrepresent a logical data value of ‘101’, the population of memory cells515 might represent a logical data value of ‘100’, the population ofmemory cells 516 might represent a logical data value of ‘000’, thepopulation of memory cells 517 might represent a logical data value of‘010’, and the population of memory cells 518 might represent a logicaldata value of ‘110’, where the right-most digit might represent thelower page data for a memory cell having a threshold voltage within thethreshold voltage range of its respective population of memory cells,the center digit might represent the upper page data for that memorycell, and the left-most digit might represent the extra page data forthat memory cell. As is understood in the art, data states of memorycells within the populations of memory cells 511-518 may be determinedby applying the read voltages r011, r001, r101, r100, r000, r010 andr110 and sensing for activation of the memory cells at the respectivevoltages in a manner similar to that discussed with reference to FIG.5A. Although a specific example of binary representation is provided,embodiments may use other arrangements of bit patterns to represent thevarious data states.

A memory cell of the population of memory cells 503 configured forstorage of overhead data (e.g., the memory cell corresponding to flag314 ₂ of FIG. 3) might be programmed to have a threshold voltage withinthe threshold voltage range corresponding to a particular one of theeight data states during the second pass of the programming operation.For example, as depicted by line 522, a memory cell of the population ofmemory cells 503, e.g., a ‘00’ logical data value, might have a desireddata state corresponding to the population of memory cells 516, e.g., a‘000’ logical data value, for the second pass of the programmingoperation. A memory cell of the population of memory cells 501, e.g., a‘11’ logical data value, configured for storage of overhead data (e.g.,the memory cell corresponding to flag 314 ₃ of FIG. 3) might also beprogrammed to have a threshold voltage within the threshold voltagerange corresponding to a particular one of the eight data states duringthe second pass of the programming operation. For example, as depictedby line 524, a memory cell of the population of memory cells 501, e.g.,a ‘11’ logical data value, might have a desired data state correspondingto the population of memory cells 516, e.g., a ‘000’ logical data value,for the second pass of the programming operation. A particular memorycell of the population of memory cells 501 configured for storage ofoverhead data (e.g., the memory cell corresponding to flag 314 ₁ of FIG.3) might be initially inhibited from programming during the second passof the programming operation, e.g., its desired data state mightinitially correspond to the population of memory cells 511, e.g., a‘111’ logical data value, for the second pass of the programmingoperation under normal operation. In this manner, the memory cellcorresponding to flag 314 ₁ of FIG. 3 having the data statecorresponding to the population of memory cells 511, e.g., a ‘111’logical data value, and the memory cells corresponding to flags 314 ₂and 314 ₃ of FIG. 3 each having the data state corresponding to thepopulation of memory cells 516, e.g., a ‘000’ logical data value, uponcompletion of the programming operation, can indicate to the memory thatthe second pass of the programming operation has been performednormally, e.g., in the absence of an indication of power loss.

If a power loss is indicated, e.g., during the second pass of theprogramming operation, an indication can be generated within the memoryto document the event. A power loss might be indicated by a controlsignal received by the memory. For example, a control signal normallyexpected to be logic high during the programming operation, such as awrite protect (WP#) control signal, might toggle to logic low if thecontroller providing that control signal loses power. In this case, thetransition of the control signal to logic low could be deemed anindication of a power loss to the memory. To document the power losswhen a power loss is indicated (e.g., deemed to have occurred), adesired data state of a particular memory cell of the page of memorycells currently undergoing the programming operation might be changedfor the remainder of the programming operation, e.g., completing theprogramming operation using power from the hold-up capacitance 138 orother energy storage device. As such, that memory cell would be expectedto have a particular data state under normal operation, e.g., a ‘111’logical data value, and would be expected to have a different data stateif a power loss is indicated, e.g., a ‘000’ logical data value.

For example, the particular memory cell of the population of memorycells 501, e.g., a ‘11’ logical data value, configured for storage ofoverhead data (e.g., the memory cell corresponding to flag 314 ₁ of FIG.3) that was initially inhibited from programming during the second passof the programming operation might have its desired data state changedfrom an expected data state for normal operation (e.g., the data statecorresponding to the population of memory cells 511, e.g., a ‘111’logical data value) to a different data state (e.g., the data statecorresponding to the population of memory cells 516, e.g., a ‘000’logical data value) for the remainder of the second pass of theprogramming operation. For example, as depicted by line 526, aparticular memory cell of the population of memory cells 501, e.g., a‘11’ logical data value, might have a desired data state correspondingto the population of memory cells 516, e.g., a ‘000’ logical data value,for a portion of (e.g., only a portion of) the second pass of theprogramming operation if a power loss is indicated. In this manner, thememory cells corresponding to flags 314 ₁, 314 ₂ and 314 ₃ of FIG. 3each having the data state corresponding to the population of memorycells 516, e.g., a ‘000’ logical data value, can indicate to the memorythat the second pass of the programming operation has been performed,but that it was completed after a power loss was indicated. It will beapparent that the data state corresponding to the flag 314 ₁ of thisexample might individually indicate that a power loss was indicated,regardless of whether the second pass of the programming operation wascompleted. In view of the foregoing example, if the data state of thememory cell corresponding to the flag 314 ₁ does not correspond to thepopulation of memory cells 511, e.g., a ‘111’ logical data value, apower loss might be deemed to have occurred during the second pass ofthe programming operation, regardless of whether its data state reachedthe desired data state corresponding to the population of memory cells516, e.g., a ‘000’ logical data value. For example, even if the energystorage device did not have sufficient stored energy to complete thesecond pass of the programming operation following a power loss, thedata state of the memory cell corresponding to the flag 314 ₁ might beexpected to experience at least some shift in threshold voltage suchthat it may not activate in response to application of the r011 readvoltage, thus providing the indication of power loss.

FIG. 6 is a flowchart of a method of operating an apparatus (e.g., amemory) according to an embodiment. At 622, a group of memory cells areiteratively programmed to respective desired data states, wherein aparticular memory cell of the group of memory cells is configured tostore overhead data (e.g., a status indicator) and a different memorycell of the group of memory cells is configured to store user data. Forexample, a write command might be received by the apparatus and includedata (e.g., user data) associated with that write command and receivedby the apparatus. The apparatus (e.g., a controller of the apparatus)might then generate data (e.g., overhead data) in response to the writecommand. In further response to the write command, the apparatus mightinitiate a programming operation to program the user data and overheaddata to a group (e.g., a page) of memory cells that includes aniterative process to shift data states of respective memory cells fromone data state (e.g., an initial or interim data state) to another datastate (e.g., a desired data state). The particular memory cell of thegroup of memory cells initially might be inhibited from programmingduring the iterative process of 622, e.g., by applying a particularvoltage level (e.g., inhibit voltage level) to a data line selectivelyconnected to the particular memory cell and configured to mitigate achange in the threshold voltage of the particular memory cell inresponse to a programming pulse.

At 624, a determination is made whether a power loss is indicated duringthe iterative process of 622. If no power loss is indicated, theiterative process of 622 can continue. The determination of 624 mightrepresent an interrupt to the iterative process of 622 responsive to aparticular indication of power loss, e.g., a particular logic level of acontrol signal, or it might represent a periodic (e.g., once everyiteration) check for an indication of power loss during the iterativeprocess of 622. If a power loss is indicated at 624, the desired datastate of the particular memory cell is changed prior to continuing withthe iterative process of 622. This might further include changing avoltage level applied to the data line selectively connected to theparticular memory cell from an inhibit voltage level to a voltage level(e.g., enable voltage level) configured to permit a change in thethreshold voltage of the particular memory cell in response to aprogramming pulse, i.e., to enable rather than inhibit programming. Uponcompletion of the iterative process of 622, e.g., passing programverification for the memory cells of the group of memory cells ordeclaring a programming failure, the process can end at 628. The datastate of the particular memory cell can indicate, in a non-volatilemanner, whether a power loss occurred during programming of the group ofmemory cells. As noted previously, an energy storage device, such ascapacitance 138 of FIGS. 1A-1B, might be used to supply a finite amountof power to the apparatus in order to seek to continue the iterativeprocess of 622 even if a power loss has occurred.

FIG. 7 is a flowchart of a method of operating an apparatus (e.g., amemory) according to another embodiment. FIG. 7 might represent thetwo-pass programming operation of TLC memory, for example. At 730, agroup of memory cells are iteratively programmed to respective interimdesired data states, wherein a particular memory cell of the group ofmemory cells is configured to store overhead data (e.g., a statusindicator) and a different memory cell of the group of memory cells isconfigured to store user data. For example, a write command might bereceived by the apparatus and include data (e.g., user data) associatedwith that write command and received by the apparatus. The apparatusmight then generate data (e.g., overhead data) in response to the writecommand. In further response to the write command, the apparatus mightinitiate a programming operation to program the user data and overheaddata to a group (e.g., a page) of memory cells that includes aniterative process to shift data states of respective memory cells fromone data state (e.g., an initial data state) to another data state(e.g., an interim desired data state). The iterative process of 730might represent the first pass of a programming operation. Theparticular memory cell of the group of memory cells might be inhibitedfrom programming during the iterative process of 730, e.g., by applyinga particular voltage level (e.g., inhibit voltage level) to a data lineselectively connected to the particular memory cell and configured tomitigate a change in the threshold voltage of the particular memory cellin response to a programming pulse.

Checking for an indication of power loss during the iterative process of730 might not be performed. For example, in a two-pass programmingoperation of TLC memory, the host or other processor providing the writecommand might not commit the data of the first pass of the programmingoperation until the second pass of the programming operation has beeninitiated. Standard firmware can track this situation and ignore thedata as invalid.

At 732, the group of memory cells are iteratively programmed torespective subsequent (e.g., final) desired data states. The iterativeprocess of 732 might represent the second pass of a programmingoperation. The particular memory cell of the group of memory cellsinitially might be inhibited from programming during the iterativeprocess of 732, e.g., by applying a particular voltage level (e.g.,inhibit voltage level) to the data line selectively connected to theparticular memory cell and configured to mitigate a change in thethreshold voltage of the particular memory cell in response to aprogramming pulse.

At 734, a determination is made whether a power loss is indicated duringthe iterative process of 732. If no power loss is indicated, theiterative process of 732 can continue. The determination of 734 mightrepresent an interrupt to the iterative process of 732 responsive to aparticular indication of power loss, e.g., a particular logic level of acontrol signal, or it might represent a periodic (e.g., once everyiteration) check for an indication of power loss during the iterativeprocess of 732. If a power loss is indicated at 734, the subsequentdesired data state of the particular memory cell is changed at 736 priorto continuing with the iterative process of 732. This might furtherinclude changing a voltage level applied to the data line selectivelyconnected to the particular memory cell from an inhibit voltage level toa voltage level (e.g., enable voltage level) configured to permit achange in the threshold voltage of the particular memory cell inresponse to a programming pulse. Upon completion of the iterativeprocess of 732, e.g., passing program verification on the memory cellsof the group of memory cells or declaring a programming failure, theprocess can end at 738. The data state of the particular memory cell canindicate, in a non-volatile manner, whether a power loss occurred duringprogramming of the group of memory cells during the second pass of theprogramming operation. As noted previously, an energy storage device,such as capacitance 138 of FIGS. 1A-1B, might be used to supply a finiteamount of power to the apparatus in order to seek to continue theiterative process of 732 even if a power loss has occurred.

FIG. 8 is a flowchart of a method of operating an apparatus (e.g., amemory) according to another embodiment. FIG. 8 provides additionaldetail as to how the iterative processes of 622 (FIG. 6) and 732 (FIG.7) might be performed. At 840, any memory cell of the group of memorycells having its desired data state for the iterative process of622/732, is inhibited from programming. At 842, a programming pulse isapplied to each memory cell of the group of memory cells. At 844, averify (e.g., program verify) is performed to determine whether memorycells of the group of memory cells have attained their respectivedesired data states for the iterative process of 622/732 in response tothe programming pulse of 842. At 846, a determination is made as towhether programming is complete, e.g., the memory cells of the group ofmemory cells have attained their respective desired data states or afailure condition has been declared. If programming is complete at 846,the process can end at 628/738. If programming is not complete at 846,any memory cell of the group of memory cells that attained its desireddata state at 844 is inhibited from further programming at 848. Avoltage level for programming pulses is changed (e.g., increased) at 850and the process returns to 842.

At 624/734, a determination is made whether a power loss is indicatedduring the iterative process of 622/732. If no power loss is indicated,the iterative process of 622/732 can continue. The determination of624/734 might represent an interrupt to the iterative process of 622/732responsive to a particular indication of power loss, e.g., a particularlogic level of a control signal. Alternatively, the determination of624/734 might represent a periodic (e.g., once every iteration) checkfor an indication of power loss during the iterative process of 622/734,such as once after determining at 846 whether programming is complete.If a power loss is indicated at 624/734, the desired data state of theparticular memory cell is changed at 626/736 prior to continuing withthe iterative process of 622, e.g., prior to proceeding to 848. Thismight further include enabling (e.g., re-enabling) programming of theparticular memory cell. Upon completion of the iterative process of622/734, e.g., passing program verification on the memory cells of thegroup of memory cells at 844 or declaring a programming failure, theprocess can end at 628/738. The data state of the particular memory cellcan indicate, in a non-volatile manner, whether a power loss occurredduring programming of the group of memory cells. As noted previously, anenergy storage device, such as capacitance 138 of FIGS. 1A-1B, might beused to supply a finite amount of power to the apparatus in order toseek to continue the iterative process of 622/732 even if a power losshas occurred.

FIG. 9 is a flowchart of a method of operating an apparatus (e.g., amemory) in accordance with an embodiment. The method of FIG. 9 might beperformed, for example, if a system flag or other indicator indicatesthat the apparatus or its host had an uncontrolled shut-down. The methodof FIG. 9 might be performed for one or more blocks of memory cells ofthe apparatus.

At 960, a determination may be made of a last written page of memorycells of a block of memory cells. At 962, a particular memory cell(e.g., corresponding to a status indicator) from the last written pageof memory cells is read to determine its data state. Reading theparticular memory cell for data output may not be available duringnormal operation of the apparatus. For example, the status indicator mayonly be available to a particular controller (e.g., an internalcontroller) of a memory performing a programming operation on the pageof memory cells. However, activating a feature to permit reading such amemory cell is well understood in the art.

At 964, a determination is made whether the data state of the memorycell is a particular data state. If the data state of the memory cell isthe particular data state at 964, the process can end at 966. If thedata state of the memory cell is not the particular data state at 964,the page of memory cells can be marked as affected by power loss at 972.For example, mapping information can be updated to indicate the statusof the page of memory cells. Optionally, if the data state of the statusindicator is not the particular data state at 964, the method mayfurther include performing error handling on user data read from thepage of memory cells. If the data is valid at 970, the process might endat 966 without marking the page of memory cells as affected by powerloss at 972.

CONCLUSION

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement that is calculated to achieve the same purpose maybe substituted for the specific embodiments shown. Many adaptations ofthe embodiments will be apparent to those of ordinary skill in the art.Accordingly, this application is intended to cover any adaptations orvariations of the embodiments.

What is claimed is:
 1. An apparatus, comprising: an array of memorycells; and a controller to perform access operations on the array ofmemory cells; wherein the controller is configured to: read a particularmemory cell of a last written page of memory cells of a block of memorycells of the array of memory cells; determine whether a thresholdvoltage of the particular memory cell is less than a particular voltagelevel; and mark the last written page of memory cells as affected bypower loss during a programming operation of the last written page ofmemory cells when the threshold voltage of the particular memory cell isdetermined to be higher than the particular voltage level.
 2. Theapparatus of claim 1, wherein the particular voltage level is configuredto activate a memory cell of the page of memory cells having an eraseddata state.
 3. The apparatus of claim 1, wherein the controller isfurther configured to: read respective data states of the memory cellsof the last written page of memory cells, including memory cellsconfigured to store user data and memory cells configured to store errorcorrection code for the user data; and perform error handling on theuser data using the error correction code for the user data.
 4. Theapparatus of claim 3, further comprising: mark the page of memory cellsas affected by power loss only if performing the error handling on theuser data fails to correct any errors detected in the user data.
 5. Theapparatus of claim 1, wherein the controller is further configured to:determine that the last written page of memory cells was programmednormally if the threshold voltage of the particular memory cell is lessthan the particular voltage level.
 6. The apparatus of claim 5, whereinthe controller is further configured to: determine that the last writtenpage of memory cells was programmed normally if the threshold voltage ofthe particular memory cell is equal to the particular voltage level. 7.An apparatus, comprising: an array of memory cells; and a controller toperform access operations on the array of memory cells; wherein, when asystem flag of the apparatus indicates that the apparatus had anuncontrolled shut-down, the controller is configured to: read aparticular memory cell of a last written page of memory cells of a blockof memory cells of the array of memory cells; determine whether athreshold voltage of the particular memory cell is less than aparticular voltage level; and mark the last written page of memory cellsas affected by power loss during a programming operation of the lastwritten page of memory cells when error handling fails to correct anyerrors detected in user data stored in the last written page of memorycells.
 8. The apparatus of claim 7, wherein the controller is furtherconfigured to: if the threshold voltage of the particular memory cell isdetermined to be higher than the particular voltage level, readrespective data states of the memory cells of the last written page ofmemory cells, including memory cells configured to store the user dataand memory cells configured to store error correction code for the userdata; and perform the error handling on the user data using the errorcorrection code for the user data.
 9. The apparatus of claim 7, whereinthe controller being configured to determine whether the thresholdvoltage of the particular memory cell is less than the particularvoltage level comprises the controller being configured to determinewhether the threshold voltage of the particular memory cell is less thanor equal to the particular voltage level.
 10. An apparatus, comprising:an array of memory cells; and a controller to perform access operationson the array of memory cells; wherein the controller is configured to:read a particular memory cell of a last written page of memory cells ofa block of memory cells of the array of memory cells; determine whethera threshold voltage of the particular memory cell is less than aparticular voltage level; and if the threshold voltage of the particularmemory cell is determined to be less than the particular voltage level,determine that the last written page of memory cells was programmednormally; and if the threshold voltage of the particular memory cell isdetermined to be higher than the particular voltage level: readrespective data states of the memory cells of the last written page ofmemory cells, including memory cells configured to store user data andmemory cells configured to store error correction code for the userdata; perform error handling on the user data using the error correctioncode for the user data; and mark the page of memory cells as affected bypower loss if performing the error handling on the user data fails tocorrect any errors detected in the user data.
 11. The apparatus of claim10, wherein the controller is further configured to determine that thelast written page of memory cells was programmed normally if thethreshold voltage of the particular memory cell is determined to beequal to the particular voltage level.
 12. The apparatus of claim 10,wherein reading the particular memory cell for data output isunavailable during normal operation of the apparatus.
 13. The apparatusof claim 10, wherein the controller being configured to determinewhether the threshold voltage of the particular memory cell is less thanthe particular level comprises the controller being configured todetermine whether the particular memory cell is storing a lowest datastate of a plurality of possible programmed data states.
 14. Theapparatus of claim 10, wherein the controller is configured to:iteratively program a group of memory cells of the array of memory cellsto respective desired data states as part of a programming operation onthe array of memory cells; determine whether a power loss to theapparatus from the power supply is indicated while iterativelyprogramming the group of memory cells to the respective desired datastates; and if a power loss to the apparatus is indicated whileiteratively programming the group of memory cells to the respectivedesired data states, change the desired data state of a particularmemory cell of the group of memory cells before continuing withiteratively programming the group of memory cells to the respectivedesired data states.
 15. The apparatus of claim 14, wherein thecontroller is further configured to: inhibit the particular memory cellfrom programming during the programming operation until determining thatpower to the apparatus is lost while iteratively programming the groupof memory cells to the respective desired data states; and enable theparticular memory cell for programming during the programming operationin response to changing the desired data state of the particular memorycell.
 16. The apparatus of claim 14, wherein the respective desired datastates are respective final desired data states, and wherein thecontroller is further configured to: iteratively program the group ofmemory cells to respective interim desired data states as part of theprogramming operation prior to iteratively programming the group ofmemory cells to the respective final desired data states.
 17. Theapparatus of claim 10, wherein the controller, in iterativelyprogramming the group of memory cells to the respective desired datastates, is further configured to: inhibit any memory cell of the groupof memory cells having its desired data state from programming; apply aprogramming pulse to each memory cell of the group of memory cells;verify whether memory cells of the group of memory cells have attainedtheir respective desired data states; determine whether programming iscomplete; and if programming is not complete: inhibit any memory cell ofthe group of memory cells attaining its desired data state from furtherprogramming; and change a voltage level for programming pulses beforeapplying a next programming pulse to each memory cell of the group offmemory cells.
 18. The apparatus of claim 17, wherein the controller isfurther configured to: determine whether a power loss to the apparatusis indicated after determining whether programming is complete andbefore inhibiting any memory cell of the group of memory cells attainingits desired data state from further programming if programming is notcomplete; and change the desired data state of the particular memorycell after determining that a power loss to the apparatus is indicatedand before changing the voltage level for the programming pulses. 19.The apparatus of claim 10, wherein the group of memory cells is a pageof memory cells of the array of memory cells, the apparatus furthercomprising: an energy storage device configured to store energy from apower supply; wherein the controller configured to continue withiteratively programming the page of memory cells to the respectivedesired data states comprises the controller being configured tocontinue with iteratively programming the page of memory cells to therespective desired data states while receiving power from the energystorage device.
 20. The apparatus of claim 10, wherein the apparatus isa solid state drive, and the array of memory cells is contained in amemory device of the solid state drive.